1. Field of the Invention
The present invention relates to a push-button switch, and more specifically concerns a push-button switch that is desirably applied to a direction-indicating switch to be attached to a wall face at an elevator hatchway so as to give a going-up or going-down indication.
2. Description of the Background Art
FIG. 14 is a cross-sectional view that shows a push-button switch which is used for a conventional direction-indicating switch for an elevator, and FIG. 15 shows an exploded perspective view thereof.
The above-mentioned push-button switch is constituted by a base member 30 having a box shape with a button hole 30a, an operation plunger 31 to be assembled in the button hole 30a, reset springs 32 that act on four corners of the operation plunger 31, a base plate 33 that is screw-connected to the base member 30 from the rear face thereof, etc., and a cap 34 made of a light-transmitting material is attached to the operation plunger 31 with a switch unit 35, an LED 36, a light-shielding case 37 having a square tube shape, etc. being assembled on the base plate 33.
The above-mentioned switch unit 35 is constituted by electrodes 38, 39 pairs of which are attached to four corners on the base plate 33, and conductive portions 41 which are attached to four portions on the lower face of a rubber operation member 40 on the base plate 33, and when the operation plunger 31 is pressed against the reset springs 32 through the cap 34, any one of operation protrusions 31a that are placed on the four corners of the operation plunger 31 is allowed to press the rubber operation member 40 so as to be shifted so that the conductive portions 41 are made in press-contact with opposing paired electrodes 38, 39 to be switched on; thus, the LED 36 is lighted on to illuminate the cap 34 while a switching output is externally supplied.
Such a conventional push-button switch has a structure in which the shift of the operation plunger 31 is guided by the inner wall face of the button hole 30a in the base member 30; therefore, in the case when a thinner structure is provided by shortening the guiding length, the pressing process of the end of the operation plunger 31 causes a one-side pressed state (one-corner pressed state) in which the operation plunger 31 is pushed and shifted in a tilted manner. Consequently, it is necessary to attach the switch units 35 to four portions so as to deal with this one-side pressed state.
When the switch units 35 are individually placed at the four portions as described above, differences tend to occur in the switching characteristics of the respective switch units 35, resulting in a difference in the operation load for turning the switch on depending on the one-side pressed portions. Moreover, since the clicking touch of the operation is obtained by the rubber operation member 40 forming the switch units 35, it is difficult to provide a sufficient clicking touch.
Moreover, the reset springs 32 of the operation plunger 31 are placed in a dispersed manner, a difference tends to occur in the deformed degree of the group of the reset springs depending on positions at which the operation plunger 31 is pressed, resulting in a different operation load.